Borna disease virus (BDV) provides an important model for the study of both the mechanisms and consequences of viral persistence in the central nervous system (CNS), a subject with important health implications given the evidence that many slowly progressive human neurological disorders may have a viral etiology. BDV has been characterized recently as a nonsegmented, negative-stranded (NNS) RNA virus with the property, unique among NNS RNA animal viruses, of a nuclear site for replication and transcription of its genome, suggesting that BDV is the prototype of a new group of animal viruses. Moreover, seroepidemiological data suggest an association between BDV and certain psychiatric disorders, which is further supported by the recent isolation of BDV from patients with major depression illness, providing further impetus for the study of this novel neurotropic infectious agent. We have cloned and determined the complete sequence of the BDV genome, and therefore, it is now possible to conduct detailed investigations dealing with the molecular biology of BDV. The first aim of this proposal is to conduct a detailed molecular analysis of the genomic organization and gene products encoded by BDV. During these studies, we will generate essential reagents, presently unavailable, for the detection and functional analysis of several BDV polypeptides. The second aim of this proposal is focused on the investigation of molecular mechanisms of BDV transcription and replication. The establishment of an in vitro systems for the synthesis of BDV mRNA will facilitate the study of BDV proteins, and possible cellular factors, involved in BDV transcription. In addition, we will utilize reverse genetic methodologies to investigate the cis-and trans-acting elements involved in BDV replication, transcription, and assembly-in vivo. The ability to reconstitute the complete BDV multiplication cycle from DNA- encoded proteins and RNAs will open the possibility in the future to conduct detailed structure-function analysis of BDV gene products in each step of its replicative cycle. The possible role of BDV in human mental disorders, together with the prospect of finding other BDV-like viruses, some of them possibly clinically relevant, underscore the importance of improving our understanding of the mechanisms of BDV persistence, and the design of effective antiviral therapies for BDV, tasks which will be facilitated by an increased knowledge of the molecular biology of BDV, which constitutes the central goal of the studies proposed.